The present invention relates to a weft detection stopper for looms, and more particularly relates to a stopper for automatically stopping a loom upon discrimination of a condemnable cloth while automatically detecting type of weft defects.
At weaving factories, manual inspection is in general applied to each woven cloth and different penalties are allocated to different defects produced on the cloth. The penalties so alloted are sequentially added to each other over the prescribed entire length of the cloth so that grading of the cloth should be fixed in accordance with the grand sum of penalties. During the manual inspection, some defects are removed by manual mending and corresponding partial sum of penalties is subtracted from the grand sum of penalties for upgrading of a condemnable cloth. That is, allocation of penalties to defects is conventionally carried out manually.
It is also conventionally employed to manually stop a loom on finding of a defect on a cloth during production so that, when possible, the defect should be removed by manual mending during the dwell of the loom. However, stopping a loom during production tends to generate a weft stripe on the cloth and lowers production efficiency of the loom. Further, manual mending causes an increase in total labour for production. An idea has recently been developed in which neither stopping of a loom nor manual mending should preferably be arranged even when any defects appear on a cloth during production as long as the presence of such defects does not cause the production of a condemnable cloth.
On the basis of such a new idea, various devices have been proposed to detect appearance of weft defects during production on a loom and stop the loom in reference to the result of detection. In any case, however, only the number of defects which appear are detected for accumulation and the loom is automatically stopped when the accumulation exceeds a given allowable limit, a threshold value.
As mentioned already, weft defects of different types have different extents of quality damage and weft defects of different types appear quite at random during production of a cloth. It is assumed that a same threshold value is set for two different cloths. One cloth includes 10 weft defects of relatively small extents of quality damage and another cloth includes 10 weft defects of relatively large extents of quality damage. Then, the cloths are the same in the number of weft defects but different in grand sum of penalties. Different grading should correctly be applied to these cloths because of the difference in grand sum of penalties. In the case of the above-described conventional systems, grading is based on the number of weft defects whilst disregarding difference in extent of quality damage. So, as long as the two cloths are the same in total number of detects per a given unit length, the cloths are graded equally. In other words, the conventional systems cannot carry out grading of a cloth whilst taking into consideration the extents of quality damage by defects. As a consequence, the conventionally proposed automatic inspection systems are all very incomplete in quality control when compared with the manual, visual inspection.